1. Field of the Invention
The present invention relates to a data transmission method and apparatus, and in particular to a protection method and apparatus for a data transmission to a communication carrier which provides wide-area LAN services or the like.
2. Description of the Related Art
In wide-area LAN services, corporate LANs are mainly connected, so that a main signal security or guarantee by a duplex mechanism is important. For attaining the main signal guarantee, a main signal redundant configuration such as an N:1 protection system or 1:1 protection system is adopted, so that communications are performed with a protection line even if a fault has occurred in a main line, thereby protecting the main signal and securing reliability of a data transmission. It is to be noted that in the following description, each of the main line and the protection line denotes a physical line.    1. N:1 Protection System: FIG. 28
In the above-mentioned N:1 protection system, a redundant configuration is formed with a single protection line for N sets of main lines. In the example of N=3 shown in FIG. 28, main lines L1-L3 are connected to main line ports W1-W3 of transmission apparatuses 200_1 and 200_2, and a protection line L4 is connected to protection line ports P1, thereby totally forming a transmission line L.    2. 1:1 Protection System: FIGS. 29-34
On the other hand, in the 1:1 protection system, a redundant configuration is formed with a single protection line for a single main line. In the example shown in FIG. 29, the main lines L1-L3 are respectively connected to the main line ports W1-W3, and protection lines L4-L6 are respectively connected to protection line ports P1-P3.
It is to be noted that in either system, the main line and the protection line are composed of lines with the same bandwidth.
Hereinafter, the 1:1 protection system will be described in more detail by referring to FIGS. 30-34.    2. 1. Arrangement: FIG. 30
FIG. 30 shows an arrangement of the transmission apparatuses 200_1 and 200_2 (hereinafter, occasionally represented by a reference numeral 200) in FIG. 29. The functions of the portions are as follows.                Reception Port Selector 1:        
The reception port selector 1 manages the information of a port which is presently valid within the main line/protection line ports (W1-W3 and P1-P3) of the redundant configuration, and transfers only a frame received at the valid port to a policing portion 2. Accordingly, when a fault has occurred in the main line, a protection line which forms the redundant configuration with the main line is set as a valid port.                Policing Portion 2:        
The policing portion 2 performs policing, and transfers the frame to a switching portion 3.                Switching Portion 3:        
The switching portion 3 determines a transmission port based on a destination MAC address of the frame, and transfers the frame to a shaper portion 5_1 and a redundant frame transmitter 40.                Redundant Frame Transmitter 40:        
The redundant frame transmitter 40 copies the frame, and transmits the copied frames from the main line port and the protection line port respectively through the shaper portions 5_2 and 5_3.                Shaper Portion 5 (5_1 and 5_3):        
The shaper portion 5 performs shaping and transmits the frame.                Command Accepting Portion 6:        
The command accepting portion 6 notifies, according to an input command, the information thereof to a redundant configuration manager 70 and the shaper portion 5.                Redundant Configuration Manager 70:        
The redundant configuration manager 70 manages redundant configuration settings (setting contents) by the command input information with a redundant configuration management table TBL1, and notifies the redundant configuration settings to the reception port selector 1 and the redundant frame transmitter 40.
It is to be noted that although a reception port and a transmission port without a redundant configuration are connected to the policing portion 2 and the shaper portion 5_1, they are not specifically related to the protection system of the present invention, so that the description of such ports will be omitted in the following description.    2. 2. Operation Example: FIGS. 31-34
Hereinafter, the operation of the portions will be described referring to FIGS. 31-34.    1) Frame Transmission from Protection Line Port: FIGS. 31 and 32
Firstly, the operation up to forming redundant configurations 1-3 by the transmission apparatus 200_1 will be described referring to FIG. 31.
The command accepting portion 6 which has received a command for forming the redundant configuration 1 with a transmission port S1 to the main line L1 being made the main line port W1 and a transmission port S4 to the protection line L4 being made the protection line port P1 notifies settings to the redundant configuration manager 70. The redundant configuration manager 70 notifies to the redundant frame transmitter 40 a redundant configuration No.1, the main line port S1, and the protection line port S4 for the transmission port.
It is to be noted that while the redundant configuration manager 70 performs transmission port processing and reception port processing, only the transmission port processing will now be described for simplifying the description, where the reception port processing will be described in the following 2).
Similarly, the command accepting portion 6 receives commands for forming the redundant configuration 2 with a transmission port S2 being made the main line port W2 and the transmission port S4 being made the protection line port P2, and the redundant configuration 3 with a transmission port S3 being made the main line port W3 and the transmission port S4 being made the protection line port P3. The operation in this case is the same as the case of forming the redundant configuration 1.
The case of transmitting a frame received at a reception port R1 of the transmission apparatus 200_1 shown in FIG. 31 from the main line port W1 (transmission port S1) and the protection line port P1 (transmission port S4) as the redundant configuration 1 will now be described.
The frame received at the reception port R1 is transferred to the policing portion 2. The policing portion 2 performs policing the frame to be transferred to the switching portion 3. The switching portion 3 determines the transmission port S1 (redundant configuration 1) based on the destination MAC address of the frame, and transfers the frame to the redundant frame transmitter 40.
The redundant frame transmitter 40 copies the frame, and transfers the copied frames respectively to the shaper portion 5_2 of the main line port W1 (transmission port S1) and the shaper portion 5_3 of the protection line port P1 (transmission port S4: protection line L4). Then, the shaper portions 5_2 and 5_3 perform shaping the frames to be transmitted.
In the case of the transmission ports determined by the switching portion 3 being ports of the redundant configurations 2 and 3, the copied frames are transmitted from the protection line ports P2 (transmission port S5: protection line L5) and P3 (transmission port S6: protection line L6) respectively as in the case of the redundant configuration 1. FIG. 32 shows a frame transmission state at this time from all of the redundant configurations of the transmission apparatus 200_1.    2) Frame Reception at Protection Line Port: FIG. 33
Hereinafter, the operation up to forming the redundant configurations 1-3 by the transmission apparatus 200_2 shown in FIG. 33 will be described.
The command accepting portion 6 having received a command for forming the redundant configuration 1 with the reception port R1 being made the main line port W1 and the reception port R4 being made the protection line port P1 notifies settings to the redundant configuration manager 70. The redundant configuration manager 70 notifies to the reception port selector 1 the redundant configuration No. 1, the main line port R1, and the protection line port R4, as to the reception port. While the redundant configuration manager 70 performs both of the transmission port processing and the reception port processing, only the reception port processing will now be described since the transmission port processing has been already described in the above-mentioned 1).
Similarly, the redundant configuration 2 is formed with the reception port R2 as the main line port W2 and with the reception port R5 as the protection line port P2, and the redundant configuration 3 is formed with the reception port R3 being made the main line port W3 and the reception port R6 being made the protection line port P3. The operation in this case is the same as the case of forming the redundant configuration 1.
Hereinafter, an operation up to transmitting (transferring) the frame received at the main line port W1 (reception port R1) and the protection line port P1 (reception port R4) of the redundant configuration 1 of the transmission apparatus 200_2 shown in FIG. 33 from the transmission port S1 will be described.
As for the frame received at the main line port W1 (reception port R1), the reception port R1 is notified to the reception port selector 1 of the redundant configuration 1, and then the frame is transferred. Since the reception port notified is the reception port R1 without a fault occurrence, the reception port selector 1 determines that the port is a current valid port of the redundant configuration 1, and transfers the frame to the policing portion 2. The policing portion 2 performs policing the frame to be transferred to the switching portion 3. The switching portion 3 determines the transmission port S1 based on the destination MAC address, and transfers the frame to the shaper portion 5_2 of the transmission port S1. The shaper portion 5_2 performs shaping the frame to be transmitted from the transmission port S1.
On the other hand, as for the frame received at the protection line port P1 (reception port R4), the reception port R4 is notified to the reception port selector 1 of the redundant configuration 1, and then the frame is transferred. Since having recognized that the valid reception port of the redundant configuration 1 is the reception port R1, the reception port selector 1 determines that the notified port is not the current valid port of the redundant configuration 1 since the notified reception port is the port R4, so that the frame is discarded.    3) Frame Reception Upon Fine fault: FIG. 34
Hereinafter, an operation up to transmitting the frame received at the protection line port P1 (reception port R4) from the transmission port 1 when a fault has occurred in the main line port W1 (reception port R1) of the redundant configuration 1 of the transmission apparatus 200_2 shown in FIG. 34 will be described.
The frame received at the protection line port P1 (reception port R4) is transferred to the reception port selector 1 of the redundant configuration 1. Having recognized that the valid reception port of the redundant configuration 1 is this time the reception port R4 due to the line fault occurrence, the reception port selector 1 determines that the notified reception port 4 is the current valid port of the redundant configuration 1, and transfers the frame to the policing portion 2. The policing portion 2 performs policing the frame to be transferred to the switching portion 3. The switching portion 3 determines the transmission port S1 based on the destination MAC address of the frame, and transfers the frame to the shaper portion 5_2 of the transmission port S1. The shaper portion 5_2 performs shaping the frame to be transmitted from the transmission port.
Also in the cases of the protection line port P2 (reception port R5) of the redundant configuration 2 and the protection line port P3 (reception port R6) of the redundant configuration 3, the reception port R5 or R6 is notified to the reception port selector 1 of the redundant configuration by the same operation as the case of the redundant configuration 1, for transferring the frame. Since the notified port is the port R5 or R6, the reception port selector 1 determines that neither port is the current valid port of the redundant configurations 2 or 3, and discards the frame. FIG. 34 shows a frame reception state at this time.
It is to be noted that there are an ATM communication network and a fault restoration method by which a fault restoration message cell is transmitted from an incoming exchange and information is exchanged in an autonomous and distributed manner upon fault of the exchange, a network state is notified to a transmitting exchange, routes are switched over, and a route fault due to the fault of the exchange is restored by a VC route level (see e.g. patent document 1). [Patent document 1] Japanese Patent Application Laid-open No. 9-18492
There have been problems in the prior art technologies as follows:
In lines forming the redundant configuration by the N:1 protection system, when a fault occurs in the main line W2 in a state where the protection line P1 is used due to the fault of the main line W1 as shown in FIG. 35, the main signal of the main line W2 can not be guaranteed since the protection line P1 has been already used.
On the other hand, in lines forming the redundant configuration by the 1:1 protection system, when a fault occurs in the main line, the main line is always guaranteed by the protection line since the main line and the protection line exist in a 1:1 correspondence manner. However, while 10 main lines+a single protection line=11 lines are required for the N:1 protection system when a redundant configuration of e.g. 10 lines is desired to be formed, 10 main lines+10 protection lines=20 lines are required for the 1:1 protection system.
Thus, in the case of the N:1 protection system, it is impossible to switch all of the main lines. On the other hand, in the case of the 1:1 protection system which can switch all of the main lines, the protection lines for the number of protections are required, which leads to a problem that construction cost is increased.